class Solution:
    def reverseString(self, s: List[str]) -> None:
        """
        Do not return anything, modify s in-place instead.
        """
        length=len(s)-1
        temp="0"
        for i in range(len(s)//2):
            temp=s[i]
            s[i]=s[length-i]
            s[length-i]=temp